The invention relates to a tilling device for tilling ground surfaces, as well as to a method for tilling ground surfaces.
Tilling devices are known from prior art that comprise at least one support device, such as a roll or wheels, for example, which supports a machine frame on the ground. A plurality of piercing tools is provided, which tools are coupled with the machine frame and are adapted to be moved up and down relative to the machine frame, whereby they can be pushed into and pulled from the ground. Further, an adjustment device is frequently provided that adjusts the distance between the support means and the machine frame in the height direction in order to adjust the depth of the penetration of the tools into the ground.
From the European Patent Publication EP-A-0037595, a tilling device is known which has two carrying arms guided in a parallelogram-like manner, one end of which pivotably holding a tool holder, whereas the other end is pivotably supported at the machine frame. A pushrod of a crank drive is hinged to the tool holder and drives the same, so that the tool holder performs an up-and-down movement. One of the two carrying arms is variable in length and comprises a stop spring means. As long as the piercing tool is outside the soil, the carrying arm rests on the stop due to the force of the spring. With the piercing tool pushed into the ground and the tilling device moving forward, the tool and the tool holder pivot against the traveling direction and the length-variable carrying arm is extended against the spring force.
However, there is a disadvantage that in case of an uneven, in particular bumpy surface and with a small piercing depth, the tools partly do not pierce the ground, whereby a part of the ground cannot be worked.